218 
ON THE EXTERNAL CAUSES OF DISEASE. 
It cannot be surprising that such an atmosphere must act 
immediately on the blood, impair its vitality, deprive it of its 
red colour, and thereby render it unfit to stimulate the heart and 
other organs through which it circulates; unfit, also, to supply 
materials for the different secretions, and to renovate the different 
tissues of the body, as well as to sustain the energy of the brain,— 
offices which it can perform only while it retains its vermilion 
colour and arterial properties. Digestion, respiration, circula¬ 
tion, secretion, and all the other functions, must act with dimi¬ 
nished power and activity in such an atmosphere. Hence all the 
functions of the body soon become sluggish and irregular, and 
the whole system loses its tone and energy. 
The sudden transitions which those horses must undergo who 
are constantly exposed to such hot-beds of filth and disease, from 
heat to cold, and vice versa , from cold to heat, must render them 
peculiarly liable to inflammation of the lungs and catarrhal af¬ 
fections of every description ; also, to those epidemic diseases 
which we have already mentioned,—diseases that may be said to 
be conveyed on “ the wings of the wind/’ and whose changes 
and circumstances are only known by their effects. 
In the organs most essential to life, we find the continual 
breathing a foul and polluted atmosphere very commonly attest¬ 
ed ; producing, in the brain, staggers and apoplexy ; in the lungs, 
hepatization, tubercles, and vomicae; in the stomach*, indiges¬ 
tion with all its train of evils; and in the liverf, it vitiates the 
bile, and produces such changes in its structure, as to be one of 
* We have frequently remarked a kind of balance between respiration 
and digestion ; and he who is an attentive observer of horses in a healthy, as 
well as diseased state, must have noticed that there is a certain balance 
between the quantity of vital air received into the lungs, and of food which 
can be digested in the stomach. 
t We are certain that the livers of horses are oftener diseased than most 
persons are aware of, and the principal cause is, a hot and ill-ventilated stable. 
High heat, particularly when accompanied with a poisoned atmosphere, is 
almost sure to produce disease in the biliary organs. This is particularly 
seen in the human subject, chiefly in those situations where there is stag¬ 
nant water to be acted on by heat. The same appearance is observed in 
cattle that are stall-fed. In most of the animals that have died with this dis¬ 
ease, under our care, the livers, instead of being a dark red colour, were of a 
pale brown, assuming the appearance of boiled liver; the entire structure 
was broken down and destroyed,with scarcely any vestige ofthe natural struc¬ 
ture remaining. These cases shew to what an extent disease may go in the 
organ before life is destroyed; for generally, in these cases, the animal appears 
in good health and condition previous to the attack. By close inquiries, 
however, we shall oftentimes find, although they have kept their condition, 
that, generally speaking, they are bad feeders, and oftentimes break out 
into cold sweats and shivering after a journey, particularly if cold water is 
given to them before they are perfectly dry. Thus the symptoms, unfor¬ 
tunately for us, arc very indistinct. 'The inflammation, being of a chronic 
